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Date: Mon, 29 Jul 2013 12:28:24 +0200
Message-ID: <CAKfTPtDBJUy6smFuACjQNVywQUiQs_iPMFs9T6uCwJOX5f7e8w@mail.gmail.com>
Subject: Re: [RFC][PATCH 1/2] ARM64: add cpu topology definition
From: Vincent Guittot <vincent.guittot@linaro.org>
To: Sudeep KarkadaNagesha <Sudeep.KarkadaNagesha@arm.com>
Cc: Hanjun Guo <hanjun.guo@linaro.org>,
        "linaro-kernel@lists.linaro.org" <linaro-kernel@lists.linaro.org>,
        Graeme Gregory <graeme.gregory@linaro.org>,
        Al Stone <al.stone@linaro.org>, Patch Tracking <patches@linaro.org>,
        Catalin Marinas <Catalin.Marinas@arm.com>,
        linaro-acpi <linaro-acpi@lists.linaro.org>,
        Will Deacon <Will.Deacon@arm.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Tomasz Nowicki <tomasz.nowicki@linaro.org>,
        Naresh Bhat <naresh.bhat@linaro.org>,
        Russell King <rmk+kernel@arm.linux.org.uk>,
        LAK <linux-arm-kernel@lists.infradead.org>
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On 29 July 2013 12:15, Sudeep KarkadaNagesha
<Sudeep.KarkadaNagesha@arm.com> wrote:
> On 29/07/13 10:46, Vincent Guittot wrote:
>> On 27 July 2013 12:42, Hanjun Guo <hanjun.guo@linaro.org> wrote:
>>> Power aware scheduling needs the cpu topology information to improve the
>>> cpu scheduler decision making.
>>
>> It's not only power aware scheduling. The scheduler already uses
>> topology and cache sharing when  CONFIG_SCHED_MC and/or
>> CONFIG_SCHED_SMT are enable. So you should also add these configs for
>> arm64 so the scheduler can use it
>>
> Just for my knowledge, I thought power aware using SCHED_MC/SMT was
> removed. I see commit 8e7fbcbc22c12414bcc9dfdd683637f58fb32759 "sched:
> Remove stale power aware scheduling remnants and dysfunctional knobs"
> I may be missing something here.

It's a common mistake to mixed SCHED_MC and powersaving balance with
SCHED_MC. Only the powersaving policy has been removed but the
SCHED_MC and SCHED_SMT are always in the scheduler and gives perf
improvement on arm 32bits

>
> Regards,
> Sudeep
>
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